Charts of Series with a lot of unknown data become too slow

[Víctor de Buen Remiro]

If we build these series in TOLBase, s1 and s2 are charted very fast, in less than 1 second. However s3 takes a long time until it's displayed.

Date from = y2000;
Date until = y2009;

Serie s1 = SubSer(Gaussian(0,1,C),from,until);
Serie s2 = SubSer(0+CalInd(WD(1)+WD(3)+WD(5)+WD(7),C),from,until);
Serie s3 = IfSer(s2,s1,?);

If we show a table or we make any other calculation there is no difference in evaluation time between these series.